1. Field of the Invention
This invention relates in general to test plugs, and more particularly, to test plugs for General Electric (G.E.) type drawout relays and meters.
2. Prior Art
In power plants, substations and large industrial plants, there exists drawout case relays and meters (hereafter referred to as relays or relay systems). The majority of such relays utilize a General Electric drawout case such as illustrated in FIGS. 1 and 1A. In such a typical configuration there will exist panels containing many such relays. The relay cases are connected to the system circuitry with permanent interconnecting wiring within the relay panel. The relays are plugged into the drawout relay cases and connections are accomplished when the normal connector plugs are inserted in the connector plug slots.
These relay systems require initial and periodic relay and relay circuit testing. A test plug for use with G.E. type drawout case relays has been on the market for over thirty years. This prior art plug provides the ability to perform testing; however, operation is very difficult, time consuming, and dangerous to system equipment, circuits, and personnel. The prior art test plug requires extensive, complicated, specific wiring to perform a single test. Each additional test normally requires removal of the plug from the relay, followed by rewiring, reconnection, and reinsertion of the plug into the relay. The rewiring and reconnection procedures are very specific for each test to be conducted and for each type and make of relay. Incorrect wiring can cause: (1) false tripping of the power system, (2) opening of CT circuits resulting in very dangerous over voltages which can be fatal to personnel and cause extensive damage to equipment, and (3) inaccurate or misleading test results.
One particular problem with the prior art test plugs is that they utilize external shorting jumpers to complete the relay circuits. Not only can these jumpers become loose from vibration, but also not infrequently they are accidentally left off, both of which problems can result in dangerous consequences.